 Galactic multiwavelength astronomy

Galactic multiwavelength astronomy compares observations of the Milky Way in different parts of the electromagnetic spectrum to distinguish its overlapping physical components. The neutral-hydrogen 21-centimeter line traces neutral atomic gas, carbon monoxide spectral lines trace molecular clouds, and infrared emission reveals warm interstellar dust and stars hidden at visible wavelengths. Radio waves from synchrotron radiation trace energetic electrons in magnetic fields, while X-rays reveal hot plasma and compact sources. Maps of the same sky region can therefore test whether a feature is a stellar concentration, an obscuring cloud or shocked gas. Comparing them also requires attention to differing angular resolution and foreground absorption.^[ref]